VulnerabilityPublished 1 Apr 2026

CVE-2026-4748: FreeBSD · Use of Incorrect Operator

Affects FreeBSDSource GCVE Database

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Not known to be exploited · CVSS 7.5 High.

Data as of 12 Nov 2026, 00:47 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CISA-ADP	CVSS 3.1	7.5

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 1 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 11 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Freebsdfreebsd/freebsd`pkg:deb/freebsd/freebsd`Other threats	Affected =15.0-RELEASE =14.4-RELEASE =14.3-RELEASE	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Until a fix is available, users should review pf configurations for rules using the address range syntax and consider rewriting them using the address[/mask-bits] syntax, which is not affected. Monitoring for vendor updates and applying official patches when released is recommended.

Description

CVE-2026-4748 is a vulnerability in FreeBSD's packet filter (pf) where a regression in hash calculation causes rules with address range syntax (x.x.x.x - y.y.y.y) that differ only in the address ranges to be silently dropped as duplicates. This results in only the first such rule being loaded, potentially causing unexpected behavior including overblocking or underblocking of network traffic. Some action keywords like 'log', 'return tll', or 'dnpipe' may also be affected, though such configurations are unlikely. Ranges using the address[/mask-bits] syntax are not impacted.

Impact

The silent ignoring of affected pf rules can cause network traffic filtering to behave unexpectedly, potentially allowing unauthorized traffic (underblocking) or blocking legitimate traffic (overblocking). This undermines firewall policy enforcement and could expose systems to network-based risks or disrupt normal operations. The CVSS score of 7.5 (high) reflects the significant confidentiality impact due to potential unauthorized access, though integrity and availability impacts are not indicated.

CWE-480Use of Incorrect Operator (opens in a new tab)
Base weaknessLikelihood of exploit: Low
The product accidentally uses the wrong operator, which changes the logic in security-relevant ways.
CWE-754Improper Check for Unusual or Exceptional Conditions (opens in a new tab)
Class weaknessLikelihood of exploit: MediumOWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product.
Requirements · Language Selection
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation
Check the results of all functions that return a value and verify that the value is expected.
Implementation
If using exception handling, catch and throw specific exceptions instead of overly-general exceptions (CWE-396, CWE-397). Catch and handle exceptions as locally as possible so that exceptions do not propagate too far up the call stack (CWE-705). Avoid unchecked or uncaught exceptions where feasible (CWE-248).
OWASP Cheat Sheets
Logging (opens in a new tab)
Error Handling (opens in a new tab)
OWASP ASVS 4.0.3
V11.1.7 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-1023Incomplete Comparison with Missing Factors (opens in a new tab)
Class weakness
The product performs a comparison between entities that must consider multiple factors or characteristics of each entity, but the comparison does not include one or more of these factors.

References

security.freebsd.org/advisories/FreeBSD-SA-26:09.pf.asc (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 12 Nov 2026, 00:47 UTC

WeaknessesCWE-480, CWE-754, CWE-1023

Technical details

References

Community reviews

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